sumps are actually pretty easy to understand once you get the general concept. all it really is is an extra container for storing more water. most use a regular tank and put it in their stand, and use an overflow box with pvc
pipe to carry water down to the sump, and a regular pump to pump the water back up to the tank.
for a very simple sump, all you need is a container, some people just use a rubbermaid container you can pick up anywhere for like 5 bucks, a pump, cost depends on how much water you plan to move through, an overflow box, probably the most expensive thing you'll need, and of course the plumbing parts, all in all you can really get away with paying around $100 if you want to be really cost efficient.
we set up one with a 10 gal
tank for about that price. HTH